Ignition device for explosive charges

ABSTRACT

An ignition device for igniting explosive charges comprises a rigid combustible material having a high burning velocity and a low-energy detonating fuse disposed on an axis therein, the ignition device containing no black powder.

ilniied Siaies Paieni Brocart Aug. 19, 1975 IGNITION DEVICE FOR EXPLOSIVE [56] References Cited CHARGES UNITED STATES PATENTS Inventor: Alain Brocari, Bergerac, France 3,103,884 9/1963 Ciccone et a1 102/27 X 3,249,049 5/1966 Zimmerman 102/46 [73] Asignee' des Poudres 3,264,993 8/1966 De Fries et a1 102/38 cc Exploslfs, Paris, France Filedi y 1969 Primary liraminer-Verlin R. Pendegrass [21] APP] N0: 822,413 Attorney, Agent, or FirmBucknam and Archer [30] Foreign Application Priority Data [57] ABSTRACT May 17, 1968 France 68.152244 An ignition device for igniting explosive Charges comprises a rigid combustible material having a high burn- [52] US. Cl 102/27 R; 102/70 R; 102/DIG. 1 ing velocity and a low-energy detonating fuse disposed [51] Int. Cl. F42b 7/00 on an axis therein, the gn n device n in ng no [58] Field of Search 102/38, 38 CC, 39, 46, black powder.

6 Claims, 1 Drawing Figure PATENTED AUB'I 9 3975 IGNITION DEVICE FOR EXPLOSIVE CHARGES This invention relates to ignition devices for igniting explosive charges, particularly explosive charges in combustible cartridge cases and solid propellant missiles.

Satisfactory ignition of explosive devices is a critical factor in the efficiency of performance of the charge. For example, satisfactory operation of solid propergols depends very largely upon the initial phase of combustion i.e. upon the ignition of the propergol block.

Conventional ignition devices, which have a fuse or a primer tube and which are filled with black powder, are not wholly satisfactory. One reason for this is that black powder is a complex mixture that quality of which may vary considerably, thus affecting the operation of the ignition devices and leading to non-reproducibility and uncertain results. Furthermore, black powder itself is particularly difficult, especially as regards safety, to manufacture and use.

We have now found that very satisfactory ignition devices can be made which do not include black powder. In particular, we have found that the black powder may be replaced by a particular type of rigid material. This material can be manufactured easily and safely and its use enables satisfactory and reproducible results to be obtained. Furthermore, since the rigid material is selfsupporting, the envelope conventionally used for con taining black powder is no longer necessary and the new ignition devices are, consequently, useful in partly or fully combustible cartridge cases and in powder blocks for self-propelled missiles.

According to the invention, we provide an ignition device comprising a body of a rigid combustible material of high burning velocity having a low-energy detonating fuse disposed therein, the fuse being connected to a primer by means of a priming system.

Preferably, the body is of tubular form and the lowenergy detonating fuse is disposed along its major axis, the tubular body being rigidly secured to a base member which is provided with means for securing the member in a cartridge-case base, the base member bearing the primer and the priming system for the fuse.

A wide range of rigid combustible materials can be used for the purposes of this invention according to the burning and mechanical properties required. A general characteristic shared by many of these materials, however, is the heterogeneity of their structure, comprising as they do fuel elements having a high burning velocity and, in adj ition, a material which has a lower burning velocity but which imparts mechanical strength to the body as a whole.

One example of a rigid combustible material useful in the igniters of the invention comprises one or more felt members comprising a high percentage (70 to 90 percent) of nitrocellulose having a nitrogen content of from 12.6 to 14.1 percent as the fuel element of high burning velocity and a low percentage to 30 percent) of cellulose together with a resin binder and a stabiliser as the combustible substance of lower burning speed imparting mechanical strength to the body. A metal in finely divided state can also be added to this mixture in order to accelerate the ignition of the charge. The resin binder may be an acrylic, polyvinyl, acrylonitrile, methylolated urea-formol or a forrnolmelamine resin or a combustible resin such as nitrocellulose or polyvinyl nitrate; the binder preferably being used in a proportion of from 5 to 15 percent. Any conventional powder stabiliser may be used with the binder, such as diphenylamine, Centralite, or nitrodiphenylamine. In the case of single-base powders, the commonest practice is to use diphenylamine in a proportion of from 0.7 to 1.2 percent, whereas with double-base powders, Centralite is used in a proportion of from 2 to 3 percent. Typical finely divided metals which may be included in the rigid combustible material are the reducing metals such as aluminium, beryllium and zirconium, the particle size being from 30 to 6011,

In order that the invention may be more fully understood an ignition device for ammunition for a mm gun will now be described, by way of illustration only, with reference to the accompanying drawing in which FIG. I is a sectional elevation view of the ignition device.

Referring now to the drawing, the ignition device comprises a tubular member 1, which is made of a rigid combustible material, along whose axis a low-energy detonating fuse 2 is disposed. Member 1 is rigidly secured to a base member 3 which is screw threaded to secure the base member in a cartridge case base. Member 3 also bears a priming system 4 for the fuse, an electric primer 5, and sealing means 6 to avoid gas leaks.

Tubular member 1 is prepared from an aqueous suspension containing 81 percent nitrocellulose (having a nitrogen content of 13.35 percent), 9 percent cellulose, 9 percent acrylonitrilic latex resin binder, and l percent diphenylamine as a stabiliser. The suspension is squeezedrained and is then introduced into a two-shell cylindrical mould (which has perforate walls) containing an axial metal rod to form an axial channel in the moulded article for the fuse. After the water has been removed by further squeezing, work-up continues by heating the mould, the tubular member being brought to a final state of apparent density 0.6. Typical dimensions of the tubular member are:

Outer diameter 20 mm Inner diameter 2 mm (i.e. diameter of the axial channel) Length 400 mm After removal of the metal rod, a 2mm diameter detonating fuse 2 is fitted into the axial channel. This fuse comprises a cylindrical lead sheath, /zmm thick, surrounding a charge of equal quantities of Penthrite and calcium silicide. The tubular member 1 and fuse 2 are then mounted on the base member 3 and are intro duced axially into a cartridge case.

The resultant charge satisfies the satutory rough-handling tests and gives improved firing results compared to a conventional primer tube; it gives less variation in the initial projectile speed with a reduced maximum pressure and with a constant initial velocity.

In the foregoing description the rigid combustible substance was moulded to form a tubular member along whose axis the detonating fuse in disposed; clearly, however, the rigid combustible substance is not limited to such a shape and can be worked into any other required shape.

For a given initial projectile velocity, when a smaller powder mass is used, the invention provides a more uniform velocity and pressure and a lower pressure than has previously been obtained. The device is well suited for high-performance equipment, especially for semi-combustible cartridge cases where the presence of an empty metal priming tube in the cartridge after ignition is undesirable. The combustible material used for this invention is relatively safe to handle during the manufacture of the device as the presence of water or resin binder and stabiliser reduces the danger of sudden explosion.

Table I lists other examples or rigid combustible substances which may be used according to the invention. The results of comparative testing against conventional devices are given in Table II.

hand fuel elements having a high burning velocity, and

on the other hand fuel elements of low burning velocity imparting mechanical rigidity to the body, in such a proportion that the resulting burning speed of the good 5 as a whole is high.

3. An ignition device according to claim 2, in which the rigid combustible material comprises one or more felt members having from 70 to 90 percent of nitrocellulose with a nitrogen content of 12.6 to 14.1 percent as the fuel element of high burning velocity, and from to percent of cellulose with a resin binder and a stabiliser as the fuel elements of low burning velocity TABLEI Composition Nitrocellulose Cellulose Resin Stabiliser Metal No. Nitrogen Proportion Nature Proportion Nature Proportion Nature Proportion Nature Proportion content l 3,4 82 Kraft 9 acrylic 8 dipl'lenyll O l amine l 3,4 75 Kraft 8 acrylic 8 diphenyll Alumin- 2 2 amine ium Sisal 1 poly- 5 vinyl nitrate 12.6 75 Kraft 9 poly- 8 Central- 3 0 3 vinyl ite forrnol poly- 5 vinyl nitrate TABLE II CONVENTIONAL DEVICE DEVICE ACCORDING TO THE INVENTION Nomenclature Primer tube Black-powder-filled copper tube 372 mm long Characteristics Igniting tubular member comprising a detonating fuse. Felt tubular member (composition No. l of Table I) Fuse, 2 g/rn, 2 mm diameter Priming by primer and lead azoimide relay I claim:

1. An ignition device which comprises a low-energy energy detonating fuse, a casing about said detonating fuse, said casing consisting of a substantially rigid tubular body of a rigid combustible material of high burning velocity, said body of combustible material surrounding said detonating fuse such that said combustible material forms the sole encasement for said detonating fuse, said tubular body being self-supporting and being adapted to be disposed within a cartridge case or missile in direct contact with an explosive charge to be ignited, a base member fixedly engaged with said body, and priming means disposed within said base member in contact with said fuse.

2. An ignition device according to claim 1, in which the rigid combustible material comprises on the one imparting mechanical strength to the body.

4. A device according to claim 3 in which said resin binder is selected from the group consisting of acrylic, polyvinyl, acrylonitrile, methylolated urea-formol, formol-melamine, nitrocellulose and polyvinyl nitrate resins, and is present in an amount from 5 to 15 percent by weight.

5. A device according to claim 3, in which said stabiliser is selected from the group consisting of diphenylamine, Centralite and nitrodiphenylamine.

6. A device according to claim 5, in which said tubular body comprises, by weight, 81 percent nitrocellulose having a nitrogen content of 13.35 percent, 9 percent cellulose. 9 percent of an acrylonitrilic latex resin binder and 1 percent diphenylamine. 

1. An ignition device which comprises a low-energy energy detonating fuse, a casing about said detonating fuse, said casing consisting of a substantially rigid tubular body of a rigid combustible material of high burning velocity, said body of combustible material surrounding said detonating fuse such that said combustible material forms the sole encasement for said detonating fuse, said tubular body being self-supporting and being adapted to be disposed within a cartridge case or missile in direct contact with an explosive charge to be ignited, a base member fixedly engaged with said body, and priming means disposed within said base member in contact with said fuse.
 2. An ignition device according to claim 1, in which the rigid combustible material comprises on the one hand fuel elements having a high burning velocity, and on the other hand fuel elements of low burning velocity imparting mechanical rigidity to the body, in such a proportion that the resulting burning speed of the good as a whole is high.
 3. An ignition device according to claim 2, in which the rigid combustible material comprises one or more felt members having from 70 to 90 percent of nitrocellulose with a nitrogen content of 12.6 to 14.1 percent as the fuel element of high burning velocity, and from 10 to 30 percent of cellulose with a resin binder and a stabiliser as the fuel elements of low burning velocity imparting mechanical strength to the body.
 4. A device according to claim 3 in which said resin binder is selected from the group consisting of acrylic, polyvinyl, acrylonitrile, methylolated urea-formol, formol-melamine, nitrocellulose and polyvinyl nitrate resins, and is present in an amount from 5 to 15 percent by weight.
 5. A device according to claim 3, in which said stabiliser is selected from the group consisting of diphenylamine, Centralite and nitrodiphenylamine.
 6. A device according to claim 5, in which said tubular body comprises, by weight, 81 percent nitrocellulose having a nitrogen content of 13.35 percent, 9 percent cellulose, 9 percent of aN acrylonitrilic latex resin binder and 1 percent diphenylamine. 